ABSTRACT The Biostatistics Core Facility (BCF) of the University of Chicago Medicine Comprehensive Cancer Center (UCCCC) provides collaborative statistical support to UCCCC investigators engaged in clinical, basic, and population sciences research. The facility is currently staffed by five PhD statisticians and one masters-level statistician in addition to the Scientific and Technical Directors. The services provided by the BCF include collaboration in the formation of study designs and data analysis plans; protocol development, randomization, and statistical analysis for Phase I, Phase II, and Phase III clinical trials; assistance in the design and analysis of retrospective and prospective observational studies; and statistical collaboration on basic science and animal research projects. The BCF interacts closely with the Cancer Clinical Trials Office (CCTO) and the UCCCC Information Technology (IT) group on database development and data management procedures to ensure a high level of data quality for clinical trials and other studies conducted within the Cancer Center. The BCF also works with the Bioinformatics Core Facility (BiCF) to ensure that investigators have access to the broad spectrum of potential analytic services required for specific studies. Clarification of specific aims and hypotheses to be tested, specification of primary, secondary, and correlative endpoints, sample-size (power) calculations, and development of data analysis plans are major areas of activity during the design phase of a study. During the conduct of a study, the BCF performs interim analyses and generates accrual and adverse event reports. Upon completion of the study, the BCF performs final statistical analyses and assists in the preparation of manuscripts for publication. BCF members also conduct statistical methodological research in support of research projects conducted within the UCCCC. During 2013-2016, members of the BCF co-authored 84 collaborative publications with UCCCC investigators and published 16 statistical methods papers stimulated by studies conducted within the UCCCC and to advance the field of oncological research. The BCF also works with UCCCC investigators in the development of new grant applications. Presently, BCF staff are engaged in active support of nine NIH/NCI-funded grants (with committed percent effort), and are co-investigators on 10 cancer-related grants pending review. BCF members serve on two key UCCCC committees that comprise the Protocol Review and Monitoring System, i.e., the Clinical Trials Review Committee (CTRC) and the Scientific Accrual Monitoring (SAM) Committee. Participation on these committees ensures that all protocols and cancer-related research projects undergo rigorous biostatistical review and patient enrollment to ongoing studies is proceeding at an optimal pace. Finally, the BCF participates in teaching and mentoring activities to foster better understanding of statistical methods among UCCCC researchers. Thus, the BCF plays a major role in accomplishing the scientific aims and objectives of the UCCCC.